This invention relates to improvements in an arc welding robot control system adopting the so-called point-to-point teaching method; that is, a computer controlled playback system by which a robot is automatically moved from one to another of a plurality of points stored therein.
A conventional arc welding robot control system of the type referred to has comprised a control console including a welding initiating pushbutton and a welding suspending pushbutton, and a teaching box for teaching a robot a plurality of points to be moved by the latter. The control console has stored therein positions of those points and the welding conditions such as a welding voltage, a welding current, etc. at each of the points and has controlled the robot and therefore so as a welding torch movably secured thereto to be moved from one to another of the stored points while the torch effects the welding of the particular workpiece on a welding line as taught by the teaching box.
When the welding suspending pushbutton is depressed for some reason, the robot is put in its inoperative state and the torch travel is stopped. At the same time, the control console commands a mating electric source of arc welding power to interrupt the welding condition so as to thereby suspend the welding. This suspension of the welding has resulted in disadvantages in that weld defects such as craters occur on the workpiece, the welding torch is fused to the workpiece, the workpiece is rendered unusable, etc. Thus, the restarting of the welding might become meaningless.
Also, when the welding suspending pushbutton is depressed upon the welding torch reaching one of the stored points, the welding has not be suspended at that point and has proceded to the next succeeding point after which the torch is stopped at the latter point resulting in the suspension of the welding. Alternatively, the torch would be able to be stopped short of one of the taught or stored points and displaced to a point deviating from a section of a straight line extending between that stored point and the just preceding stored point for the purpose of observing the status of that point or correcting the position of the workpiece. Then, the depression of the welding starting pushbutton has caused the welding torch to travel along a line starting with the displaced point and running to that stored point short of which the torch has been stopped. That is, the torch has passed through a line quite different from that connecting the stored points. This has resulted in the disadvantages that the workpiece is rendered unusable because it has been welded along a line which is different from a line preliminarily taught by the teaching box and a working efficiency is very poor.